A huge, huge help. I try to use this system as much as I can when running games: both on and off my podcast. In a podcast setting it's particularly effective because we're already thinking the mindset of listening to audio: rewinding, pausing, resuming. And giving people that common language helps a ton in introducing a safety system.
I would recommend that you display it first, however. I've noticed players have a hard time taking control of a scene unless it's established it will happen without judgement.
Definitely use it.
(And to the designer: thank you so much for providing this to the community, and thank you for all the work you've done!)